This invention relates to an image scanner, particularly to an image scanner for use in reading an image of a sheet-like medium, such as a manuscript and a film.
It is a recent trend that a personal computer of high performance can be provided at a low cost. This trend makes image information processing be very popular and increases chance to deal with various image information for everyone. Under the circumstances, it is frequent that various informations including a manuscript are inputted into such a personal computer. With such a change of the circumstances, information are converted into electronic information to construct a filing system consisting of integrated information, even if the information were recorded in a paper, a photo film, or OHP (Over Head Projector) paper that has been conventionally used as a recording medium of information. Further, an Internet comes to be in common use with developments of computers or communication technology. As a result, image information has been used considerably even in a field of home page or electronic mail.
As a way of inputting such various image informations, an image scanner is used to read the image. Conventionally, image scanners are mainly classified into either reflection type image scanners or transmission type image scanners. The reflection type image scanners, which are represented by a frat bed scanner and a sheet feed scanner, read, for example, a photo printed in , a magazine, a newspaper, a printed article printed and outputted by a printer, a hand-written manuscript, and the like by a reflection light. On the other hand, the transmission type image scanners, which are represented by a film scanner to read a film such as 35 mm film, and the like, read an image recorded in a transmission manuscript such as a positive film, a negative film, and the like.
The reflection type image scanners read a manuscript by the use of a light reflected by the manuscript while the transmission type image scanners read a manuscript by the use of a light transmitted through the manuscript. In the former, namely the reflection type image scanners, the light reflected by the manuscript is to be incident into an image sensor. It is therefore necessary that both the image sensor and a light source should be positioned at one side of the manuscript commonly to each other. On the other hand, in the latter, namely the transmission type image scanners, the light transmitted through the manuscript is to be incident into an image sensor. It is therefore necessary that the manuscript should be located between a light source and the image sensor. By difference of structure thus mentioned, conventionally, these two types of image scanners are sold and used as articles different from each other,
In the interim, as described above, chance of inputting an image by an image scanner is increased. Further, it comes to be popularized that reading of image by using image scanners are carried out even in a comparatively small office and a family. However, from the viewpoints of a space for locating the image scanner and the purchase price, it is still difficult for users to acquire both the reflection type and the transmission type image scanners separately. Consequently, it is strongly desired that an image scanner having functions of both the reflection type and the transmission type image scanners is provided to users. Some proposals are made to provide such an image scanner having functions of both the reflection type and the transmission type image scanners. For example, image scanners having the both functions thereof are exemplified in unexamined Japanese Patent Publications, Hei8-88736, namely 88736/1996, and Hei4-167964, namely 157964/1992, respectively. Further, an image scanner similarly having the both functions thereof is exemplified in examined Japanese Patent Publication, Hei5-76222, namely 76222/1993. However, the image scanners disclosed in these examples have, to be sure, functions of both the reflection type and the transmission type image scanners. It is inevitably caused to occur that the image scanners become large in size.